This invention relates to a process for the preparation of hydroxyarylaldehydes from 4-alkylphenols by a new route. The invention further relates to the novel compositions that are prepared from the 4-alkylphenols. Among other uses known in the art, hydroxyarylaldehydes are particularly useful as intermediates in the preparation of oximes which find utility as metal extractants.
The end compounds produced by the processes of the present invention are particularly useful as intermediates for the production of oximes that in turn are useful for the extraction of copper and other metals from aqueous solutions. In this recovery process, the metal extractant is dissolved in a solvent, and is contacted with an aqueous metal solution to form a complex with the metal which is soluble in an organic solvent. The organic phase is then separated from the aqueous phase and the metal is stripped from the organic phase, usually by means of an acid.
The water immiscible solvents usually employed for this purpose are hydrocarbon solvents such as the petroleum-derived liquid hydrocarbons, either straight chain or branched, such as kerosene, fuel oil, etc. Various aromatic solvents may also be used, such as, for example, benzene, toluene, xylene and other aromatic solvents, particularly those derived from petroleum processing which may contain alkyl substituted aromatic materials. In addition to the simple hydrocarbon solvents, the chlorinated hydrocarbons may also be used and in some instances may improve solubility. Accordingly, both the unsubstituted and the chlorinated solvents are contemplated by the term "liquid hydrocarbon".
The extractants that are made from the intermediates that are produced by the processes of the present invention are characterized as having sufficient solubility in one or more of the above solvents or mixtures thereof to make about a 2% solution, and they are essentially insoluble or immiscible with water. At the same time, they each should form a complex with a metal, such as copper, which complex, likewise, is soluble in the organic solvent to at least the extent of about 2% by weight.
These characteristics are generally achieved by having alkyl substituents on the ring, that have at least 3 alkyl carbon atoms. Usually it is preferred not to have more than 25 carbon atoms total in the alkyl substituents since these substituents contribute to the molecular weight of the oxime extractant without improving operability. Large substituents, also, increase the amount of oxime needed for a given copper loading capacity. In general, the branched chain alkyl substituents effect a greater degree of solubility of the reagent and of the copper complex and, accordingly, these are preferred, especially those of 6 to 18 carbons.
As described in U.S. Pat. No. 4,868,334, for example, oxime extractants are often produced by reacting an organic carbonyl compound such as an aldehyde or ketone with hydroxylamine, usually generated from a hydroxylamine salt such as hydroxylammonium sulfate or hydroxylammonium chloride.
Current oximation procedures employ standard oximation processes with an alcohol such as methanol as a solvent, hydroxylammonium sulfate, and sodium acetate. An improved oximation process is described, for example, in U.S. Pat. No. 5,300,689.
The oximes, such as the hydroxy aryl ketoximes and hydroxy aryl aldoximes, which are substantially insoluble in water but soluble in water-immiscible organic solvents, such as kerosene, are useful in solvent extraction processes for the recovery of metals, particularly copper, from aqueous solutions. U.S. Pat. No. 4,507,268 describes a number of such oxime reagents prepared from ketones and aldehydes, and the use thereof in liquid/liquid extraction processes.
Reagents frequently employed in commercial processes for copper recovery are included among those offered by Henkel Corporation under the LIX.RTM. trademark, viz., LIX.RTM.63, LIX.RTM.65N, LIX.RTM.64, LIX.RTM.64N, LIX.RTM.70, LIX.RTM.71, LIX.RTM.73, LIX.RTM.34, LIX.RTM.54, LIX.RTM.605, LIX.RTM.617, LIX.RTM.622 and LIX.RTM.6022, LIX.RTM.860, LIX.RTM.984, LIX.RTM.973, and LIX.RTM.84.
Briefly noted, LIX.RTM.63 extractant includes, in addition to a liquid hydrocarbon diluent, an aliphatic .alpha.-hydroxy oxime extractant (5,8-diethyl-7-hydroxy-dodecan-6-oxime) of the type illustrated in Swanson U.S. Pat. No. 3,224,873. The LIX.RTM.65N extractant includes an alkyl substituted hydroxy benzophenone oxime (2-hydroxy-5-nonyl benzophenone oxime) as set out in Swanson U.S. Pat. No. 3,592,775. The LIX.RTM.64 extractant and the LIX.RTM.64N extractant incorporate benzophenone oxime extractants (2-hydroxy-5-dodecyl benzophenone oxime and 2-hydroxy-5-nonyl benzophenone oxime, respectively) in combination with an aliphatic .alpha.-hydroxy oxime as described in U.S. Pat. No. 3,423,449.
Formulation of the LIX.RTM.70 extractant involves the combination of a benzophenone oxime extractant containing an electron withdrawing substituent (2-hydroxy-3-chloro-5-nonyl benzophenone oxime) with an aliphatic .alpha.-hydroxy oxime. The LIX.RTM.71 and LIX.RTM.73 formulations both include a mixture of two benzophenone oximes, one of which has an electron withdrawing substituent (i.e., a mixture of 2-hydroxy-5-nonyl benzophenone oxime and 2-hydroxy-3-chloro-5-nonyl benzophenone oxime) with the latter reagent further including an aliphatic .alpha.-hydroxy oxime.
The LIX.RTM.34 extractant and the LIX.RTM.54 extractant incorporate alkaryl sulfonamido quinoline and .beta.-diketone extractants, respectively. The LIX.RTM.605 extractant, the LIX.RTM.617 extractant, the LIX.RTM.622 extractant, and the LIX.RTM.6022 extractant, on the other hand, employ alkyl substituted hydroxy benzaldoxime (salicylaldoxime) extractants according to Parrish, J. South African Chem. Inst., 23, pp. 129-135 (1970). Thus, the LIX.RTM.605 extractant and the LIX.RTM.617 extractant include 2-hydroxy-5-nonyl benzaldoxime extractants with, respectively, nonylphenol and tridecanol additives. The LIX.RTM.622 extractant and the LIX.RTM.6022 extractant comprise fomulations of 2-hydroxy-5-dodecyl benzaldoxime and a tridecanol additive in approximately 4:1 and 1:1 w/w ratios, respectively. Acorga PT-5050 extractant is offered for sale by Acorga, Ltd., Hamilton, Bermuda, as a formulation comprising 2-hydroxy-5-nonyl benzaldoxime and a tridecanol additive in an approximately 2:1 w/w ratio. See also, Ackerley et al., U.S. Pat. No. 4,020,105; Ackerley et al., U.S. Pat. No. 4,020,106; and Dalton, U.S. Pat. No. 4,142,952.
There exists a general need in the art for more efficient processes for producing such oxime extractants. In the usual processes, the hydroxyarylaldehydes may be prepared by a number of routes. A summary and review of the synthesis of aromatic hydroxyarylaldehydes may be found in H. Fiege, K. Wedemehyer, K. A. Bauer, A. Krempel and R. G. Molleken, Fragrance Flavor Subst. Proc. Int. Haarmann Reimer Symp. 2nd, 1979 (Publ. 1980), pp. 63-73, which discusses in particular three processes of preparation.
One of these processes is the Reimer-Tiemann reaction which involves the reaction of a phenol with chloroform under very basic conditions to yield the salicylaldehyde. Yields tend to be low and recovery of the product difficult. U.S. Pat. No. 4,324,922 relates to improvements in the process, citing as further background Hans Wynberg, "Chemical Reviews", Vol. 60, 169 (1960) and Ferguson, "Chemical Reviews", Vol. 38, 229 (1946). Other U.S. Pat. Nos. 3,206,513 and 3,972,945, provide further background.
A second industrially useful approach involves condensation of the phenol with formaldehyde followed by oxidation with oxygen and a catalyst. While reasonable yields of salicylaldehyde are obtained, the process consists of two steps and involves the use of expensive catalysts. Illustrative of some of the patents relating to this process are U.S. Pat. Nos. 3,173,956, 3,321,526, 3,673,257, 3,780,110, 4,026,950 and 4,190,605.
Other variations have been introduced. One which is described in U.S. Pat. No. 4,151,201, involves heating paraformaldehyde with phenol in the presence of anhydrous stannous chloride and pyridine. A second, which is described in U.S. Pat. No. 4,231,967, involves replacing the stannous chloride with an iron or chromium compound, preferably chromium acetylacetonate. Good yields are obtained via both processes. Both processes require relatively high levels of the catalyst promoter, pyridine, which must be recycled and requires special handling on an industrial scale. The use of heavy metals also presents problems in waste disposal. Further, iron and chromium compounds tend to promote adverse side reactions. A third variation which is described in U.S. Pat. No. 4,638,096, involves reacting a corresponding phenolic compound with formaldehyde in the presence of a titanium or zirconium containing catalyst.
Another process, disclosed in U.S. Pat. No. 4,085,146 directed specifically towards production of alkylsalicylaldehydes, involves formation of a Mannich base, followed by oxidation and hydrolysis to the alkylsalicylaldehyde. While good yields are said to be obtained, the process is economically burdensome due to the number of steps involved.
It is an object of the instant invention to provide a new process for making substituted hydroxyaryl aldehydes, particularly, alkyl substituted salicylaldehydes, which process affords substantial product yields.